Samba Segfault when moving/copy file from a EXT4 partition to BTRFS partition

zeroomega · 17. September 2023

Hi I noticed the Samba (ver 2:4.13.13+dfsg-1~deb11u5) in my machine running OMV 6.8.0-1 (Shaitan) will segfault whenever I tried to move or copy a file from an EXT4 partition (mapped to a Windows network drive to Z:) to an BTRFS partition (mapped as Windows network drive Y:).

The panic error from the syslog is:

Code

Sep 16 18:37:41 misato smbd[48795]: [2023/09/16 18:37:41.940638,  0] ../../lib/util/fault.c:159(smb_panic_log)
Sep 16 18:37:41 misato smbd[48795]:   ===============================================================
Sep 16 18:37:41 misato smbd[48795]: [2023/09/16 18:37:41.942504,  0] ../../lib/util/fault.c:160(smb_panic_log)
Sep 16 18:37:41 misato smbd[48795]:   INTERNAL ERROR: Signal 11: Segmentation fault in pid 48795 (4.13.13-Debian)
Sep 16 18:37:41 misato smbd[48795]: [2023/09/16 18:37:41.942568,  0] ../../lib/util/fault.c:164(smb_panic_log)
Sep 16 18:37:41 misato smbd[48795]:   If you are running a recent Samba version, and if you think this problem is not yet fixed in the latest versions, please consider reporting this bug, see https://wiki.samba.org/index.php/Bug_Reporting
Sep 16 18:37:41 misato smbd[48795]: [2023/09/16 18:37:41.942644,  0] ../../lib/util/fault.c:169(smb_panic_log)
Sep 16 18:37:41 misato smbd[48795]:   ===============================================================
Sep 16 18:37:41 misato smbd[48795]: [2023/09/16 18:37:41.942678,  0] ../../lib/util/fault.c:170(smb_panic_log)
Sep 16 18:37:41 misato smbd[48795]:   PANIC (pid 48795): Signal 11: Segmentation fault in 4.13.13-Debian
Sep 16 18:37:41 misato smbd[48795]: [2023/09/16 18:37:41.960135,  0] ../../lib/util/fault.c:274(log_stack_trace)
Sep 16 18:37:41 misato smbd[48795]:   BACKTRACE: 28 stack frames:
Sep 16 18:37:41 misato smbd[48795]:    #0 /lib/x86_64-linux-gnu/libsamba-util.so.0(log_stack_trace+0x30) [0x7f7ecb76a220]
Sep 16 18:37:41 misato smbd[48795]:    #1 /lib/x86_64-linux-gnu/libsamba-util.so.0(smb_panic+0x26) [0x7f7ecb76a486]
Sep 16 18:37:41 misato smbd[48795]:    #2 /lib/x86_64-linux-gnu/libsamba-util.so.0(+0x186a1) [0x7f7ecb76a6a1]
Sep 16 18:37:41 misato smbd[48795]:    #3 /lib/x86_64-linux-gnu/libpthread.so.0(+0x13140) [0x7f7ecb015140]
Sep 16 18:37:41 misato smbd[48795]:    #4 /usr/lib/x86_64-linux-gnu/samba/libsmbd-base.so.0(vfs_offload_token_db_fetch_fsp+0x35) [0x7f7ecb53cd65]
Sep 16 18:37:41 misato smbd[48795]:    #5 /usr/lib/x86_64-linux-gnu/samba/vfs/btrfs.so(+0x3155) [0x7f7ec65d5155]
Sep 16 18:37:41 misato smbd[48795]:    #6 /usr/lib/x86_64-linux-gnu/samba/libsmbd-base.so.0(+0x1f662c) [0x7f7ecb5f662c]
Sep 16 18:37:41 misato smbd[48795]:    #7 /usr/lib/x86_64-linux-gnu/samba/libsmbd-base.so.0(smb2_ioctl_network_fs+0x802) [0x7f7ecb5f70b2]
Sep 16 18:37:41 misato smbd[48795]:    #8 /usr/lib/x86_64-linux-gnu/samba/libsmbd-base.so.0(smbd_smb2_request_process_ioctl+0x623) [0x7f7ecb5f4233]
Sep 16 18:37:41 misato smbd[48795]:    #9 /usr/lib/x86_64-linux-gnu/samba/libsmbd-base.so.0(smbd_smb2_request_dispatch+0xe4c) [0x7f7ecb5e4c6c]
Sep 16 18:37:41 misato smbd[48795]:    #10 /usr/lib/x86_64-linux-gnu/samba/libsmbd-base.so.0(+0x1e5847) [0x7f7ecb5e5847]
Sep 16 18:37:41 misato smbd[48795]:    #11 /lib/x86_64-linux-gnu/libtevent.so.0(tevent_common_invoke_fd_handler+0x7d) [0x7f7ecb03170d]
Sep 16 18:37:41 misato smbd[48795]:    #12 /lib/x86_64-linux-gnu/libtevent.so.0(+0xda77) [0x7f7ecb037a77]
Sep 16 18:37:41 misato smbd[48795]:    #13 /lib/x86_64-linux-gnu/libtevent.so.0(+0xbc07) [0x7f7ecb035c07]
Sep 16 18:37:41 misato smbd[48795]:    #14 /lib/x86_64-linux-gnu/libtevent.so.0(_tevent_loop_once+0x94) [0x7f7ecb030df4]
Sep 16 18:37:41 misato smbd[48795]:    #15 /lib/x86_64-linux-gnu/libtevent.so.0(tevent_common_loop_wait+0x1b) [0x7f7ecb03109b]
Sep 16 18:37:41 misato smbd[48795]:    #16 /lib/x86_64-linux-gnu/libtevent.so.0(+0xbba7) [0x7f7ecb035ba7]
Sep 16 18:37:41 misato smbd[48795]:    #17 /usr/lib/x86_64-linux-gnu/samba/libsmbd-base.so.0(smbd_process+0x828) [0x7f7ecb5d38f8]
Sep 16 18:37:41 misato smbd[48795]:    #18 /usr/sbin/smbd(+0xe715) [0x55beceb18715]
Sep 16 18:37:41 misato smbd[48795]:    #19 /lib/x86_64-linux-gnu/libtevent.so.0(tevent_common_invoke_fd_handler+0x7d) [0x7f7ecb03170d]
Sep 16 18:37:41 misato smbd[48795]:    #20 /lib/x86_64-linux-gnu/libtevent.so.0(+0xda77) [0x7f7ecb037a77]
Sep 16 18:37:41 misato smbd[48795]:    #21 /lib/x86_64-linux-gnu/libtevent.so.0(+0xbc07) [0x7f7ecb035c07]
Sep 16 18:37:41 misato smbd[48795]:    #22 /lib/x86_64-linux-gnu/libtevent.so.0(_tevent_loop_once+0x94) [0x7f7ecb030df4]
Sep 16 18:37:41 misato smbd[48795]:    #23 /lib/x86_64-linux-gnu/libtevent.so.0(tevent_common_loop_wait+0x1b) [0x7f7ecb03109b]
Sep 16 18:37:41 misato smbd[48795]:    #24 /lib/x86_64-linux-gnu/libtevent.so.0(+0xbba7) [0x7f7ecb035ba7]
Sep 16 18:37:41 misato smbd[48795]:    #25 /usr/sbin/smbd(main+0x1ddf) [0x55beceb12d1f]
Sep 16 18:37:41 misato smbd[48795]:    #26 /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xea) [0x7f7ecae4dd0a]
Sep 16 18:37:41 misato smbd[48795]:    #27 /usr/sbin/smbd(_start+0x2a) [0x55beceb12eba]
Sep 16 18:37:41 misato smbd[48795]: [2023/09/16 18:37:41.960627,  0] ../../source3/lib/util.c:838(smb_panic_s3)
Sep 16 18:37:41 misato smbd[48795]:   smb_panic(): calling panic action [/usr/share/samba/panic-action 48795]
Sep 16 18:37:42 misato smbd[48795]: [2023/09/16 18:37:42.019699,  0] ../../source3/lib/util.c:845(smb_panic_s3)
Sep 16 18:37:42 misato smbd[48795]:   smb_panic(): action returned status 0
Sep 16 18:37:42 misato smbd[48795]: [2023/09/16 18:37:42.019952,  0] ../../source3/lib/dumpcore.c:315(dump_core)
Sep 16 18:37:42 misato smbd[48795]:   dumping core in /var/log/samba/cores/smbd
Sep 16 18:37:42 misato smbd[48795]:

Alles anzeigen

The panic will be resolved if I remove the `shadow:` option entries and `shadow_copy2` from the `/etc/samba/smb.conf, like the one below.

Code

[NAS2]
path = /srv/dev-disk-by-uuid-SOME-UUID/Data/
guest ok = no
guest only = no
read only = no
browseable = yes
inherit acls = no
inherit permissions = no
ea support = no
store dos attributes = no
shadow:mountpoint = /srv/dev-disk-by-uuid-SOME-UUID/
shadow:snapdir = /srv/dev-disk-by-uuid-SOME-UUID/.snapshots/
shadow:basedir = /srv/dev-disk-by-uuid-SOME-UUID/Data/
shadow:sort = desc
shadow:format = _%Y%m%dT%H%M%S
shadow:delimiter = _
shadow:snapprefix = ^NAS2\(@hourly\)\{0,1\}\(@daily\)\{0,1\}\(@weekly\)\{0,1\}\(@monthly\)\{0,1\}\(@yearly\)\{0,1\}$
shadow:localtime = no
dfree command = /usr/sbin/omv-btrfs-dfree
dfree cache time = 30
vfs objects =  btrfs shadow_copy2
printable = no
create mask = 0664
force create mode = 0664
directory mask = 0775
force directory mode = 0775
hide special files = yes
follow symlinks = yes
hide dot files = yes
valid users =
invalid users =
read list =
write list =

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I am not quite sure if it is an Samba bug or its library is just a bit old and have compatibility issue with the btrfs driver the kernel use. I was considering updating the Samba and see if it can be resolved but it looks like I will ruin my apt package dependency if I do so. Samba will not panic if I just move/copy file within the btrfs partition. It also doesn't panic if I copy/move file from my Windows workstation to the btrfs partition. It seems only an problem if the copy is from a samba managed non-btrfs partition (in my case, an EXT4 partition) to a btrfs partition. Shall I create an issue in the github issue tracker?

The "deleting shadow copy from /etc/samba/smb.conf" is also not very convenient. As the file will be rewritten by omv engine when a configuration is changed. Could we have an option in the OMV's web UI to set the shadow_copy2 to off? For me, Samba snapshot and shadow_copy is completely useless and it would be great if there is an option in the setup to disable it.

votdev · 17. September 2023

If you want to see the bug fixed, please report the issue to the Debian project. Alternatively the upstream Samba project. The OMV project is not and can't maintain the software it bundles.

Zitat von zeroomega

Could we have an option in the OMV's web UI to set the shadow_copy2 to off?

No, that is not possible.

You can add vfs objects = foo bar baz to the Extra options field of the SMB share to override the setting generated by OMV.

zeroomega · 18. September 2023

Zitat von votdev

If you want to see the bug fixed, please report the issue to the Debian project. Alternatively the upstream Samba project. The OMV project is not and can't maintain the software it bundles.

No, that is not possible.

You can add vfs objects = foo bar baz to the Extra options field of the SMB share to override the setting generated by OMV.

I will try to file a bug in debian. This issue is likely fixed in upstream Samba but didn't backport to the version that Debian uses.

I tried the Extra options workaround you mentioned. It looks like I need to put blank vfs objects = and shadow:OPTIONS = into the Extra options to make it work. After this, the copy/move option no longer causes samba to segfault.

Could you briefly explain why it is not possible to add an UI option in OMV to disable the shadow_copy2 when configurate an SMB/CIFS share for a folder on btrfs partition? IIUC the `shadow_copy2` options are added to `smb.conf` by the OMV engine and it will only do so if it detects the underlying partition is using btrfs. I didn't see the same option happen on EXT4 (it doesn't have snapshot feature anyway) or ZFS (it has snapshot feature) partition. If that is the case, adding an UI option to disable shadow_copy2 should be doable.

votdev · 18. September 2023

Zitat von zeroomega

Could you briefly explain why it is not possible to add an UI option in OMV to disable the shadow_copy2 when configurate an SMB/CIFS share for a folder on btrfs partition? IIUC the `shadow_copy2` options are added to `smb.conf` by the OMV engine and it will only do so if it detects the underlying partition is using btrfs. I didn't see the same option happen on EXT4 (it doesn't have snapshot feature anyway) or ZFS (it has snapshot feature) partition. If that is the case, adding an UI option to disable shadow_copy2 should be doable.

This is simple. I hate to add knobs for every usecase. OMV is no webmin where you can configre everything that is possible.

namitonguyen · 10. November 2023

I just formatted my drive to btrfs recently and had the same problem, this is giving me a lot of trouble, I think I'll go back to ext4 and stay away from btrfs.

zeroomega · 16. November 2023

Zitat von namitonguyen

I just formatted my drive to btrfs recently and had the same problem, this is giving me a lot of trouble, I think I'll go back to ext4 and stay away from btrfs.

In my case I encountered some I/O performance issue with btrfs lately so I switched to OpenZFS entirely.

The smb segfault only happens with shadow_copy2 enabled, which won't be enabled in anything other than btrfs.

Samba Segfault when moving/copy file from a EXT4 partition to BTRFS partition

macom 17. September 2023

votdev 17. September 2023

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